DC Generator MCQ

71. Condition for maximum power delivered in DC Generator is

1. Back EMF = (2 x Supply voltage)
   
2. Back EMF = Supply voltage
   
3. Back EMF= (Supply voltage/4)
   
4. Back EMF (Supply voltage/9)
   

72. A 4-pole, lap wound, DC generator has the following details:

Flux 0.07 Wb/pole, speed =900 r.p.m, Armature conductors= 440.

The generated e.m.f. is

1. 400 V
2. 520 V
3. 462 V
4. 900 V

73. For a dc generator, if the brushes are given a small amount of forward shift, the effect of armature reaction is

1. totally demagnetising
   
2. totally magnetising
   
3. partly demagnetising and partly cross-magnetising
   
4. totally cross magnetising

74. Under-commutation gives rise to

1. sparking at the leading edge of the brush
   
2. sparking at the trailing edge of the brush
   
3. no sparking at all
   
4. sparking at the middle of the brush

75. The commutator of a d.c. machine acts as a

1. full-wave rectifier
   
2. half-wave rectifier
   
3. controlled full-wave rectifier
   
4. controlled half-wave rectifier

76. The exciting coils of any DC machine are wound

1. in the machine
   
2. in the armature slots
   
3. around the poles
   
4. separately

77. The waveform of the armature m.m.f. in DC machine is

1. rectangular
   
2. square
   
3. sinusoidal
   
4. triangular

78. The parts of the armature electric circuit which take active part in e.m.f. generation are

1. The coil sides inside the slots
   
2. The overhangs
   
3. both the coil sides inside the slots and the overhangs
   
4. the commutator segments

79. A DC generator can be termed as

1. rotating amplifier
2. prime mover
3. power pump
4. None of these

80. An e.m.f. is induced in the windings of an armature of a DC generator when the armature rotates in…..

1. alternating magnetic flux
   
2. magnetic field
   
3. electrostatic field
   
4. electromagnetic flux